1. Field of the Invention
The present invention relates to a multi-tube type X-ray computed tomography (CT) apparatus comprising a plurality of pairs of X-ray tubes and detectors.
2. Description of the Related Art
Conventionally, an X-ray CT apparatus is designed to apply X-rays generated by an X-ray tube to a subject to be examined and detect X-rays transmitted through the subject by using an X-ray detector, thereby obtaining a tomogram by performing reconstruction processing for detected data using a computer. A multi-tube type X-ray CT apparatus is also known, in which two or more pairs of X-ray tubes and detectors are mounted on an annular rotating frame to reduce the rotation angle of the frame.
A multi-tube type X-ray CT apparatus is disclosed in, for example, Jpn. Pat. Appln. KOKAI Publication No. 2004-73406. This reference shows an apparatus which includes an X-ray tube for medical treatment and an X-ray tube for visualization. In a multi-tube type X-ray CT apparatus on which two or more pairs of X-ray tubes and detectors are mounted, direct radiation from the X-ray tube of a given pair and scattered radiation from the X-ray tube of another pair may reach the detector of the given pair. In addition, since direct radiation does not differ much in characteristics from scattered radiation, it is difficult to separate them. For this reason, the image quality of a reconstructed image is affected by scattered radiation from the X-ray tube of a pair other than the given pair.
Conventionally, in a multi-tube type X-ray CT apparatus on which two or more pairs of X-ray tubes and X-ray detectors are mounted, scattered radiation from the X-ray tube of a pair other than a given pair affects the image quality of a reconstructed image.